We've used a hand held air-born particle counter to monitor our client indoor air quality since 2003, long before the current generation of HEPA filters became available. We purchased the particle counter with the thought of mostly using it to quantify for our clients the difference in air quality, including airborne allergens, between our methodology and the industry standard. Early on, we chanced into a demonstration of how useful the device could be in monitoring our crew's performance month to month (we provide janitorial service in Phoenix AZ).
In our first round of client visits taking air quality readings, we found two buildings, both serviced by the same crew, that had readings, in the one micron and larger range (the size of most allergens), three to four times what we'd expected. Pulled the crew in for a conversation and an equipment check; found the one micron filter in place, but ruptured. Cleaned out the vacuum, replaced the filter, had a somewhat more intense conversation with the crew, and, within three weeks, we had the readings down to the expected range.
Now that we have 0.3 micron HEPA filters available, we do even better.
It's awfully useful, being able to quantify one's results.
A bit about us:
My firm, CBN Building Maintenance, provides commercial cleaning services in Phoenix AZ and the wider metro area. We've been in business since 1974; hold the BBB's A-plus rating; and have long been in the forefront of the industry in environmentally sensitive cleaning for health, safety and security. Our program can generally improve Indoor Air Quality, in the size range of most allergens, by a factor of 50%, as reflected in our ongoing IAQ sampling.